1. Field of Invention
The present invention relates to a position-control device for a light modulation device, which controls the position of the light modulation device and is used for manufacturing an optical unit including a plurality of the light modulation devices and a combining optical system for combining light modulated by each of the light modulation devices. The present invention also relates to a position-controlling method using the position-control device and an initial-position controlling jig.
2. Description of Related Art
Currently, projectors can include a plurality of light modulation devices (liquid crystal panels) that modulate separate colored light component in accordance with image data, a color-combining optical system (crossed dichroic prism) which combines colors modulated by the plurality of light modulation devices, and a projection optical system (projection lens) for projecting the light combined by the color-combining optical system for forming projection images have been used.
With such projectors, a so-called three-plate-type projector, for example, is generally known in which light emitted from a light source is decomposed into three colored light RGB by a dichroic mirror, the three colored light components are modulated in accordance with image data by three respective liquid crystal panels, the modulated light is combined by a crossed dichroic prism, and color images are projected via a projection lens.
In order to obtain a clear projection image by such a projector, the position of each liquid crystal panel must be controlled accurately when the projector is manufactured so as to avoid variations in the position of pixels between each liquid crystal panel and variations in distance from the projection lens between each liquid crystal panel. Therefore, focus control for positioning each liquid crystal panel at the position of the back focus of the projection lens and alignment control for the pixels of each liquid crystal panel to coincide with the pixels of other liquid crystal panels are performed by using a position-control device.
Currently, in a known technology, the focus and alignment control is performed in such a manner that the relative positions of the liquid crystal panels are controlled by using the position-control device with an optical unit, as the object to be controlled, which includes three liquid crystal panels, a crossed dichroic prism, and a projection lens, in which: (1) the optical unit is mounted to the position-control device and light is applied to an image-forming region of each liquid crystal panel; (2) a projection image is displayed on a screen via the crossed dichroic prism and the projection lens; (3) the light of the projection image reflected from the screen is captured by a detecting device such as a CCD camera which moves within or is fixed at a given position; and (4) the positions and the like of the focus and the pixels of each liquid crystal panel which are detected by the CCD camera are confirmed.
However, there is a problem with the above-describe systems in that the operation of position-control is laborious work in which the optical axis of the projection lens must be positioned every time the optical unit including the three liquid crystal panels, the crossed dichroic prism, and the projection lens is mounted to the position-control device, the projection lens being large compared with the other components, such as the liquid crystal panels, and the crossed dichroic prism, and thereby being difficult to handle.
The position control of the CCD camera is performed by moving the CCD camera with respect to a projection image which is actually displayed on a screen. Therefore, it can take a long time for detection and the like by the CCD camera, whereby there is a problem in that the position-control operation is laborious.
Accordingly, an object of the present invention is to provide a position-control device for a light modulation device, a position-controlling method for controlling the position of the light modulation device, and an initial-position controlling jig so that the position-control operation can be easily performed.
According to a first invention of the present application, a position-control device for a light modulation device, which is used in the manufacture of an optical unit including a plurality of the light modulation devices and a combining optical system for combining the light modulated by each light modulation device, and which controls the positions of the light modulation devices, can include a reference projection optical system which projects the light combined by the combining optical system to form a projection image and has a predetermined optical characteristic, the reference projection optical system being built in the position-control device so as to be commonly used.
In the position-control device according to the invention which is provided with the reference projection optical system built therein, it is not necessary to align the optical axes every time the position of the light modulation device is controlled, for example, when the optical axes are once aligned when building in, and only the replacement of the light modulation device and the combining optical system is required, whereby the position-control operation can be easily performed.
Since the position of the optical axis of the reference projection optical system is fixed, the positions of the detecting device and the like, for example, which detect the data of a projection image displayed on a screen via the reference projection optical system, may be fixed after setting the same, whereby the position-control operation can be easily performed.
The reference projection optical system is preferably selected from a plurality of projection optical systems and preferably has an average optical characteristic.
In this case, the optical characteristic can include a depth of focus, individual focal distances of the projection optical systems, a chromatic aberration, variations in the optical axes, trapezoidal distortion, and the like. An average optical characteristic can be computed from the optical characteristic of each projection optical system, and a projection optical system having an optical characteristic similar to the computed optical characteristic is used as the reference projection optical system.
When a projection optical system having a very large depth of focus is used as the reference projection optical system or a projection optical system having a very small depth of focus is used as the reference projection optical system when controlling the position of the light modulation device, the projection optical system to be prepared when manufacturing a projector must be a particular projection optical system which has a depth of focus the same as that of the projection optical system used for the position control, whereby the manufacturing operation becomes complex due to the laborious work. However, when a projection optical system having an average optical characteristic selected from a plurality of the projection optical systems is used as the reference projection optical system, it is no longer necessary to prepare a projection optical system having a particular optical characteristic, thereby improving manufacturing efficiency of the projection optical system, whereby the manufacture of the projector is performed easily and the efficiency of the manufacture is greatly improved.
According to a second invention of the present application, a method for controlling the position of a light modulation device is provided, which can use a position-control device for controlling the position of the light modulation device, the position-control device being used in the manufacture of an optical unit including a plurality of the light modulation devices and a combining optical system for combining the light modulated by each light modulation device, the position-control device projecting the light combined by the combining optical system to form a projection image displayed on a screen via a projection optical system and detecting data of the projection image displayed on the screen by at least one detecting device, thereby controlling the positions of the light modulation devices. The method can include controlling an initial position of each light modulation device such that the light modulation device is moved so that the position of the optical center of the light modulation device coincides with a reference position which has been set in advance, and lighting a light source for generating light to be applied to the light modulation devices. The method can further include controlling the position of the detecting device such that the detecting device is moved along the screen in accordance with the data of the projection image projected on the screen with the light being lighted in the step of lighting the light source; controlling the focus of the detecting device, and controlling the positions of the light modulation devices after controlling the focus of the detecting device in the focus controlling step.
According to the invention, since the detecting device is moved in accordance with the data of the projection image before the position of the light modulation device is controlled, the time for moving the detecting device can be reduced compared with a case in which the detecting device is moved when controlling the position of the light modulation device. Accordingly, the time required for the position-control operation is reduced and the position-control operation can be easily performed.
According to a third invention of the present application, a method for controlling the position of a light modulation device is provided, which can use a position-control device that controls the position of the light modulation device, the position-control device being used in the manufacture of an optical unit including a plurality of the light modulation devices and a combining optical system for combining the light modulated by each light modulation device, in which the position-control device projects the light combined by the combining optical system to form a projection image. The position-control device can include a reference projection optical system having a predetermined optical characteristic and being built in the position-control device so as to be commonly used, and at least one detecting device for detecting data of the projection image displayed on a screen via the reference projection optical system. The method can include controlling an initial position of each light modulation device such that the light modulation device is moved so that the position of the optical center of the light modulation device coincides with a reference position which has been set in advance, automatically controlling the position of the detecting device such that the detecting device is automatically moved along the screen in accordance with the position of the optical axis of the reference projection optical system, which has been set in advance, lighting a light source for generating light to be applied to the light modulation devices, and controlling the positions of the light modulation devices after controlling the position of the detecting device in the step of automatically controlling the position of the detecting device.
According to the invention, the detecting device is moved in accordance with the position of the optical axis of the reference projection optical system set in advance, whereby the detecting device can be moved without display of the projection image on the screen. Accordingly, it is not necessary to light the light source. With this arrangement, the detecting device can be easily moved, and the position-control operation can be easily performed.
According to a fourth invention of the present application, an initial-position-controlling jig can be in the position-controlling method described above, for setting the reference position of the light modulation device. The position controlling jig can include a dummy combining optical system, as a dummy of the combining optical system, provided with holes in a side face of the dummy combining optical system, and a dummy light-modulation-device, as a dummy of the light modulation device, provided with insertion terminals to be inserted into the holes.
In this case, the light modulation device is preferably moved by a position-control mechanism which moves the light modulation device in accordance with the data detected by the detecting device.
The position-control for the position-control mechanism can be performed by disposing the dummy combining optical system at a predetermined position, and moving the position-control mechanism mounted with the dummy light modulation device so as to insert the insertion terminals of the dummy light modulation device into the holes of the dummy combining optical system.
According to the invention, a plurality of the types of, for example, position-controlling jigs are prepared according to the corresponding types of the projector, and the positions of the position-control mechanisms corresponding to the types of the projector are registered in advance in the position-control device, whereby it is not necessary to control the position of the position-control mechanism when the position of the light modulation device is controlled and the position-control mechanism must be simply moved to the position registered in advance when controlling the position of the light modulation device. Therefore, the position-control operation is easily performed.
According to a fifth invention of the present application, an initial-position-controlling jig used in the position-controlling method described above, for setting the reference position of the light modulation device, can include a rectangular parallelepiped glass body as a dummy of the combining optical system. The glass body is provided at the light-incident end face with a reference-position-indicating mark for indicating on the screen the designed reference position of the detecting device.
According to the invention, when light is applied to the glass body and the light is displayed on the screen via a projection optical system, the reference-position-indicating mark provided on the glass body is displayed as a silhouette on the screen. In this state, the detecting device can be easily disposed at the designed reference position by moving the detecting device to the silhouette, whereby the position-control operation can be easily performed.